Methods and Protocols

      Aerosol Droplet Size Distribution Measurement Instruments


      Published on
      Oct 15, 2016

      One important property to be evaluated in smoke-free products that generate an aerosol – such as heated tobacco products and e-cigarettes – is the distribution of aerosol droplet sizes. The size and distribution of the droplets determine where they are deposited in the human respiratory tract, with larger particles depositing in the upper and large airways, while smaller particles deposit deeper in the lungs.


      Details updated on May 24, 2023.

      Mini-MOUDI impactor

      The instrument named Mini-MOUDI impactor, which replaced our previous PIXE cascade impactor, allows to classify aerosol droplet size on the collection plates. From this, it is possible to determine how the aerosol mass is distributed over the measured size range and to extract a single representative size parameter – the mean mass median aerosol diameter, often abbreviated M(MMD) – which is useful to evaluate product performance and risk evaluation for toxicological purposes. To perform such evaluation, an instrument is used under Good Laboratory Practice to ensure scientific quality and data traceability. 

      Read the publication: Evaluation of the Tobacco Heating System 2.2. Part 2: Chemical composition, genotoxicity, cytotoxicity, and physical properties of the aerosol


      Laser Aerosol Spectrometer – Droplet size distribution for e-cigarette platforms

      Measuring instantaneous droplet sizes is not possible with the MOUDI impactor because analysis of each collection plate needs to be done offline, usually by measuring mass accumulated on each plate over the course of the experiment. In contrast, the Laser Aerosol Spectrometer allows to overcome this limitation at the expense of requiring a more dilute aerosol sample. Laser aerosol spectrometry is most useful in the initial phases of product development.

      We set up the instrument to specifically measure e-cigarette type products, allowing to determine whether the aerosol droplet size is within the required specifications. Product development continues until reaching target product performance. To this end, a complete and novel methodology was developed using the state-of-art tool Laser Aerosol Spectrometer.

      Read the publication: A Scattering Methodology for Droplet Sizing of E-Cigarette Aerosols